Operational electrode impedance measurement for an implantable medical stimulator

ABSTRACT

Controller, system and method for an implantable medical device having a plurality of electrodes, said implantable device being capable of delivering a therapeutic stimulation to a patient. An electrode interface is operatively coupled between a plurality of electrodes and a control module. The control module uses an electrode interface to obtain a plurality of measurements of impedance values for a plurality of selected pairs of individual ones of the plurality of electrodes. A user interface displays an indicia, indicative of operability of a group of at least one of said plurality of electrodes, based on a comparison of said plurality of measurements to a predetermined range, said indicia being a qualitative representation of operability of said group of at least one of said plurality of electrodes.

RELATED APPLICATION

This application claims priority to provisional U.S. Application Ser.No. 60/840,642, filed Aug. 28, 2006.

FIELD

The present invention is related generally to implantable medicalstimulators and, more particularly, to implantable medical stimulatorshaving electrode impedance measurement capability.

BACKGROUND

The medical device industry produces a wide variety of electronicdevices for treating patient medical conditions using electricalstimulation. Depending upon the medical condition, medical devices canbe surgically implanted or connected externally to the patient receivingtreatment. Clinicians use medical devices alone or in combination withdrug therapies and surgery to treat patient medical conditions. For somemedical conditions, medical devices provide the best, and sometimes theonly, therapy to restore an individual to a more healthful condition anda fuller life. Examples of implantable medical devices designed todeliver therapeutic electrical stimulation include neurologicalstimulators and spinal stimulators as well as pacemakers anddefibrillators.

Implantable medical devices configured to deliver therapeutic electricalstimulation commonly deliver therapy via electrodes positioned on one ormore leads and operatively connected to the implantable medical device.In some instances, the housing of the implantable medical device mayalso serve as an electrode or an electrode may be positioned on thehousing. The leads and electrodes are commonly positioned in thepatient's body during the same surgical procedure in which theimplantable medical device is implanted.

The positioning of leads and electrodes is often an inexact procedureand commonly may be dependent on the particular physiologiccharacteristics of the patient. In addition, leads and electrodescommonly may be positioned within the patient without the medicalprofessional conducting the procedure being capable of actually seeingwhere the leads are positioned—instead, external aides such asfluoroscopes and endoscopes commonly may be employed to inform themedical professional as to an approximate location of the leads.

Due to the inherent uncertainty involved in the placement of leads andelectrodes for an implantable medical device, implantable medicaldevices and the external controllers that interface with the devices arecommonly operable to perform a test on the leads and electrodes toverify that the leads and electrodes are functioning properly and arepositioned correctly. A common test is to check the impedance betweenpairs of electrodes. One electrode will transmit a signal with knownelectrical characteristics. Another electrode will sense the transmittedsignal, and using known, fundamental electrical relationships thedifferences between the transmitted and sensed electrical signals areused to compute the impedance between the two electrodes. The measuredimpedance value can give a medical professional information relating towhether the electrodes involved in the test are positioned correctly andworking properly.

An external controller, or programmer, is commonly utilized in leadimpedance tests. The programmer provides a user interface via a displayscreen, and is manipulated by a medical professional via a variety ofinputs, such as buttons and touchscreens. The programmer commonlycommunicates with the implantable medical device via inductivetelemetry, though communication protocols utilizing far-field radiofrequency technology medical device to interface with electrodesconnected with the implantable medical device in order to obtainmeasurements of impedance values of each associated electrode. Thevalues of electrode impedance may then be displayed to a medicalprofessional and a judgment as to the efficacy of each electrode maythen be made.

In order to accomplish this, a coil, operatively coupled to thecontroller, typically by a wire, is placed over a coil operativelycoupled to the electronics in the implantable medical device, therebyestablishing an inductive telemetry link over which data may be passedin either direction.

For example, United States Patent Application Publication No,2006/0036186, Goetz et al, Automatic Impedance Measurement of anImplantable Medical Device, discloses a method and controller forautomating impedance measurements. An entry for each electrode pair isdisplayed on a user interface. Each electrode pair entry includes anidentification of electrodes for an electrode pair, an associated valueof impedance, and a value of current that is measured between theelectrodes of a pair.

Another example, U.S. Pat. No. 5,891,179, Er et al, Method and ApparatusFor Monitoring and Displaying Lead Impedance in Real-Time For anImplantable Medical Device, discloses a method and controller fordisplaying real-time graphical representations of variable leadimpedance. Impedance values are calculated using Ohm's law or otherrelated equations. Then the calculated impedance values are output to agraphic display for presentation thereby in graphical form or are outputto a graphic printer, or both.

Another example, United State Patent Application Publication No.2003/0114899, Samuelsson et al, Programming System For Medical Devices,discloses a method and controller for displaying graphicalrepresentations of a quantity influenced by the operation of a medicaldevice. Such quantities may include information derived from tests anddiagnostics, such as an electrode impedance test.

Another example, United States Patent Application Publication No.2005/0033385, Peterson et al, Implantable Medical Device ProgrammingApparatus Having a Graphical User Interface, discloses graphicaldisplays of the operation of a medical device, such as a test of adevice lead. Results are organized according to the anatomical positionof the lead, i.e., whether the lead is an atrial or ventricular lead,allowing the clinician to efficiently assess the functionally of alllead data by virtue of its grouping into precise anatomical categories.

Another example, U.S. Pat. No. 6,721,600, Jorgenson et al, ImplantableLead Functional Status Monitor and Method, discloses a system forobtaining trend data on the status of leads of an implantable medicaldevice. The lead status measurement derives its data from varioussources including lead impedance, non-physiologic sensed events,percentage of time the device is in mode switch, the results of capturemanagement operation, sensed events, reversion paced counts, andrefractory sense counts. The lead status measurement employs a set ofweighted sum rules used by algorithms to process data from all of theabove-mentioned sources to arrive at easily interpreted messagesaccessible to clinicians via an external programmer. Data from thesesources identify lead conductor/connector interface issues andelectrode/tissue interface issues indicative of lead-related mechanismssuggestive of impending or actual lead failure. The weights are“interpreted” for the user in the following manner.

-   -   Lead-related parameters are all within range or operating        normally.    -   One or more of the lead parameters are out-of-range. Investigate        leads.    -   A number of lead parameters are out-of-range and a safety        problem exists.

Messages to the User refer to three types of lead-related conditions:

lead/conductor/connector messages, lead insulation messages, andbiological interface messages. Examples of such messages include:

-   -   High impedance (>4000 ohms, 2× increase over reference, among        others).    -   Increase in threshold(s) above preset or programmed limit.    -   Reduction in R and P-wave amplitude below preset or programmed        limit.

Useful, summary information from a variety of trend data are thereforepresented for the use of a medical professional.

SUMMARY

A medical professional may compare the impedance value measured in anelectrode-to-electrode impedance test with a known operable range orwith other criteria. If the measured impedance value is within thespecified criteria, e.g., the operable range, it is likely the electrode(including the lead) is functional and properly placed. If the measuredimpedance value is outside of the operable range, it is likely that theelectrode (including the lead) is not functional, not properly placed orboth. Because the operable range or other criteria for the value ofelectrode impedance may be known to the manufacturer of the implantablemedical device, it may not be necessary in many situations to compel themedical professional to manually compare the measured impedance with theoperable range.

An embodiment of the present invention uses a controller toautomatically perform a comparison of electrode impedance with a knownoperable range and report the functional status of the electrodes(including the leads) based on that comparison. Providing a “go/no-go”indication to the user greatly simplifies the testing procedure and issignificantly quicker. In addition, the actual measured impedance valuesmay also be displayed.

A complete lead impedance test will commonly involve testing eachelectrode with every other electrode. This amount of information iscommonly required to diagnose faults in electrode placement. The numberof individual tests that must be preformed for a complete test thereforeincreases exponentially for every added electrode, thereby increasingthe time required to run the test, which may commonly be performed in asterile, operating room environment. An embodiment of the presentinvention tests the impedance of each electrode only twice, exclusivelyto determine if there are any faults with the electrodes. If all of theimpedance measurements are within the operable range, it may beunderstood that the tested leads are functional and the electrodes areproperly placed. Thus, any individual electrode whose impedance valuetest indicates that the electrode is operational need not be testedagain. Remaining, non-tested electrodes may then be tested incombinations involving other non-tested electrodes and omitting testedelectrodes may greatly simplify and speed the testing procedure.

Lead impedance testing is typically preformed with a physicianprogrammer, which can be bulky and can take a considerable period oftime, e.g., several minutes, to power up and become operational. Inaddition, it may be that the physician programmer should be operatedoutside of the sterile field in the operating room. An embodiment of thepresent invention replaces the physician programmer, for electrodetesting purposes, with a light, battery powered, fast-booting, hand-heldcontroller that powers up in a considerably shorter period of time thanthe physician programmer, e.g., within seconds, and that may be usedwithin the sterile field, saving several minutes in the running of thetest. In addition, because the controllers are light and simple to use,the controllers may be given to patients to perform impedance tests intheir own homes.

In an embodiment, the present invention provides a controller for animplantable medical device having a plurality of electrodes, theimplantable device being capable of delivering a therapeutic stimulationto a patient, having a control module, a user interface providingcontrol of the control module by a medical professional, and anelectrode interface operatively coupled between the plurality ofelectrodes and the control module. The control module uses the electrodeinterface to obtain a plurality of measurements of impedance values fora plurality of selected pairs of individual ones of the plurality ofelectrodes, and the user interface displays an indicia, indicative ofoperability of a group of at least one of the plurality of electrodes,based on a comparison of the plurality of measurements to apredetermined range, the indicia being a qualitative representation ofoperability of the group of at least one of the plurality of electrodes.

In an embodiment, the indicia is a first indicia, and wherein the userinterface displays a second indicia upon a different result of thecomparison.

In an embodiment, the user interface displays the first indicia if thecomparison determines that all of the plurality of measurements ofimpedance values are within the predetermined range.

In an embodiment, the user interface displays a second indicia if thecomparison determines that any of plurality of measurements of impedancevalues outside of the predetermined range.

In an embodiment, one of the plurality of electrodes is included notmore than twice in the plurality of measurements of impedance values ofselected ones of the plurality of electrodes.

In an embodiment, each of the plurality of electrodes is included notmore than twice in the plurality of measurements of impedance values ofselected ones of the plurality of electrodes.

In an embodiment, the plurality of measurements of impedance values areconducted for fewer than all of the plurality of electrodes.

In an embodiment, the plurality of measurements of impedance values areconducted only for those of the plurality of electrodes that are in usefor the therapeutic stimulation.

In an embodiment, the implantable medical device further comprises aplurality of leads, each of the plurality of electrodes being associatedwith one of the plurality of leads, wherein each of the plurality ofelectrodes of each individual one of the plurality of selected pairs ofelectrodes are associated with the same lead, and wherein the controlmodule uses the electrode interface to obtain a plurality ofmeasurements of impedance values for the plurality of selected pairs.

In an embodiment, the patient has a brain having two hemispheres, eachof the plurality of electrodes being associated with one of thehemispheres, wherein each of the plurality of electrodes of each of theplurality of selected pairs of electrodes are associated with the sameone of the hemispheres of the brain.

In an embodiment, each individual one of the plurality of electrodes isassociated with two of the plurality of selected pairs, and wherein thesecond indicia is displayed for an individual one of the plurality ofelectrodes only if each of the measurements of impedance of theplurality of selected pairs with which the individual one of theplurality of electrodes is associated are outside of the predeterminedrange.

In an embodiment, the present invention further provides a systemcapable of delivering a therapeutic stimulation to a patient, having animplantable medical device having a plurality of electrodes capable ofdelivering the therapeutic stimulation to the patient, and a controller,operatively coupled to the implantable medical device,. The controllerhas a control module, a user interface providing control of the controlmodule by a medical professional, and an electrode interface operativelycoupled between the plurality of electrodes and the control module. Thecontrol module uses the electrode interface to obtain a plurality ofmeasurements of impedance values for a plurality of selected pairs ofindividual ones of the plurality of electrodes, and the user interfacedisplays an indicia, indicative of operability of a group of at leastone of the plurality of electrodes, based on a comparison of theplurality of measurements to a predetermined range, the indicia being aqualitative representation of operability of the group of at least oneof the plurality of electrodes.

In an embodiment, the system further comprises a remote station, theremote station being operatively coupled to the controller, theimplantable medical device being operatively coupled to the remotestation via far-field radio frequency communication.

In an embodiment, the remote station comprises a remote station userinterface, the remote station user interface displaying the indicia tothe user.

In an embodiment, the present invention further provides a method fordelivering therapeutic stimulation to a patient using an implantablemedical device having a plurality of electrodes. The method has thesteps of obtaining a plurality of measurements of impedance values for aplurality of selected pairs of individual ones of the plurality ofelectrodes, and displaying an indicia based upon a result of acomparison of the plurality of measurements of impedance values with apredetermined range. The indicia is indicative of operability of a groupof at least one of the plurality of electrodes, the indicia being aqualitative representation of operability of the group of at least oneof the plurality of electrodes.

DRAWINGS

FIG. 1 illustrates an external controller used in conjunction with aimplantable medical device;

FIG. 2 illustrate the implantable medical device of FIG. 1 withassociated electrodes;

FIG. 3A is an illustration an external controller intended to be used inconjunction with the implantable medical device of FIG. 1;

FIG. 3B is an illustration of buttons positioned on a side of theexternal controller illustrated in FIG. 3A;

FIG. 3C is a screenshot of the external controller illustrated in FIG.3A which is set to begin conducting a lead connection check;

FIG. 3D is a screenshot of the external controller illustrated in FIG.3A having recently conducted a lead connection check;

FIG. 4 is a functional block diagram of the external controller of FIG.3; and

FIG. 5 is a flow chart illustrating function of an embodiment of thepresent invention.

DETAILED DESCRIPTION

The entire content of provisional U.S. Application Ser. No. 60/840,642,filed Aug. 28, 2006, is hereby incorporated by reference.

FIG. 1 shows the general environment of an embodiment of implantablemedical device 20. Implantable neurological stimulator 22 is shown, butother embodiments such as pacemakers and defibrillators and the like arealso applicable. Implantable neurological stimulator 22 is implantedsubcutaneously in side 28 of patient 30, generally at a depth of between1.0 and 2.5 centimeters, dependent on factors such as the patient'sphysiology and the nature of the therapy to be delivered. Lead 24 isoperatively coupled to implantable neurological stimulator 22 at header26. Lead 24 is positioned along spinal cord 31 of patient 30. Controller32, also called a patient programmer, may become transcutaneouslycoupled to implantable neurological stimulator 22 via an inductivecommunication link through the tissue of patient 30 through antenna 34when antenna 34 is placed in proximity to implantable neurologicalstimulator 22. Though the precise maximum range for establishing aninductive communication link will vary depending on such factors asavailable battery power and the physical characteristics of coil 70(FIG. 4), antenna 34 should generally be placed within six (6)centimeters of implantable medical device 22. If an inductivecommunication link has been established then communication may proceeduntil the communication is ended either by controller 32, or by breakingthe communication link, commonly by increasing the distance betweenantenna 34 and implantable neurological stimulator 22 beyond the rangeat which communication may occur.

In an embodiment, controller 32 is small enough to be held comfortablyin the hand of a typical adult, where it may be easily manipulatedeither with that hand or the user's other hand. Controller 32 may bedurable enough to be sterilized and brought within a sterile fieldenvironment and durable enough to be dropped without becomingnon-functional.

FIG. 2 shows a closer view of implantable neurological stimulator 22 andlead 24, operatively coupled by optional extender 36. Electrodes 38 aremounted on distal end 37 of lead 24. Electrodes 38 are comprised of aconductive material, in an embodiment, metal, that come into directcontact with tissue of patient 30. Electrodes 38 are operatively coupledwith implantable neurological stimulator 22 via header 26 through wirescomprised of conductive material that pass through the interior of lead24 and are operatively coupled with conductive wires in the interior ofextender 36. A cutaway of implantable neurological stimulator 22 showssecondary coil 23 which may create an inductive communication link withprimary coil 70 (FIG. 4).

The number of leads 24 associated with implantable neurologicalstimulator 22, and the number of electrodes 38 associated with each lead24, may depend on the nature and location of the therapy implantableneurological stimulator 22 is intended to deliver. The configuration ofeight electrodes 38 per lead 24 may commonly be utilized in spinal cordstimulation applications which may typically include two sucheight-electrode 38 leads 24. Such a configuration may be common inapplications based around the electrical stimulation of comparativelylong, narrow regions of patient 30. By contrast, applications whichrequire the stimulation of regions comparatively planar or spread out,such as deep-brain stimulation, may utilize up to four leads 24 of infour-electrode 38 per lead 24 configuration.

Commonly, each lead 24 associated with implantable neurologicalstimulator 22 may be identical to each other lead 24. In order tofacilitate programming and testing, electrodes 38 are commonly assigneda unique alpha-numeric identifier, commonly a unique integer startingwith “0” and proceeding up. In an embodiment with sixteen electrodes 38,then, each electrode 38 would be assigned an integer identifier from “0”through “15”. In this embodiment, the proximal electrode 38 on one ofleads 24 may be assigned the identifier “0”, the next most-proximateelectrode 38 “1”, and so on, from proximate to distal along the lead.When all of electrodes 38 on lead 24 have been assigned an identifier,another lead 24 is selected and the proximal-to-distal assignment ofidentifiers continues until all electrodes 38 on all leads 24 have beenassigned an identifier. In an embodiment, to further facilitateorganization and testing of electrodes 38 and leads 24, electrodes 38are then organized into groups of four electrodes 38. Electrodes 38assigned identifiers “0” through “3” would be assigned to a first group,electrodes 38 assigned identifiers “4” through “7” would be assigned toa second group, and so on until all electrodes 38 have been assigned toa group. In an embodiment, four groups may be created.

Additionally, embodiments of the present invention are envisioned forapplications that substitute other types of implantable medical devicesfor implantable neurological stimulator 22, such as pacemakers anddefibrillators. In these embodiments, leads 24 may be of significantlydifferent configuration from those utilized by implantable neurologicalstimulator 22. In an embodiment utilizing an implantable defibrillator,leads may include pacing leads 24 with a pair of pacing electrodes 38 aswell as defibrillation leads 24, potentially including bothdefibrillation and pacing electrodes 38.

FIG. 3A shows controller 32. Display 52 displays both text and graphicalpresentations of data and menus to a user to allow the user to control,in some respects, implantable neurological stimulator 22, and to obtainvarious types of information from implantable neurological stimulator22. Buttons 54 may provide the primary interface for the user to controlthe functionality of controller 32 and implantable medical device 22. Invarious embodiments the number, positioning and nature of buttons 54differs dependent on the nature of implantable medical device 22 and thetherapy implantable medical device 22 is configured to deliver. Forexample, in the embodiment depicted in FIG. 3A, primarily utilized fordeep brain stimulation, it may be undesirable to allow a user very muchcontrol over the functionality of implantable medical device 22. Becausethe user is given relatively little means for impacting implantablemedical device 22 performance, there may be relatively little need formany interface buttons 54. Thus, buttons 54 are limited only to two atthe top of the screen, utilized for accessing functions, and the fourarrow buttons 54 at the bottom of controller 32, used for scrollingamong menus, as well as a power button.

By contrast, in an embodiment depicted in FIG. 3B, in some applicationsit may be desirable for the user to exert more control over the functionof implantable neurological stimulator 22, and thus buttons 54 on theside of controller 32 are provided. An example of such a situation whereincreased user control may include spinal stimulation, as illustrated inFIG. 1. The extra buttons 54 may allow a user added control over theamount of electrical stimulation delivered by implantable neurologicalstimulator 22

FIG. 3C depicts a screenshot 55 of controller 32 to begin conducting aLead Connection Check, or “LCC”. In an embodiment, the screen 55 may bearrived at by pressing and holding both top buttons 54 for threeseconds. Once screen 55 is arrived at, the user may commence the LCC bypressing one or more of buttons 54, depending on the various embodimentsof controller 32. In an embodiment, graphic 57 on display 52 indicatesto the user which button to press. In an embodiment illustrated in FIG.3C graphic 57 indicates that the user should press the sync button (seeFIG. 3B) in order to commence the LCC.

FIG. 3D depicts a screenshot 59 of the results display from a recentlyconducted LCC.

In the illustrated embodiment, the display identifies that the LCC testhad just occurred, as well as a qualitative indication of the result ofthe LCC, in this case illustrated as a textual indicia of the number ofelectrodes 38 that had passed the test (see FIG. 5). In alternativeembodiments, results may report the number of electrodes that failed topass, or may provide graphical indicia of the result of the LCC test.Such graphical indicia may include a mark corresponding to eachelectrode, the mark indicating either a pass or a fail, or charts, suchas a pie chart or a bar with a length corresponding to the number ofelectrodes 38 that had passed the test.

In an embodiment, a characteristic of the above described embodiment isthe distinction these embodiments make between indicia that indicate aqualitative result, rather than indicating a quantitative resultcorresponding to the actual measure of impedance between each pair ofelectrodes 38. The above-described embodiments provide the advantage ofa simple to understand result, compared with a quantitative result thatmust be interpreted against the predetermined range for passage of thevarious impedance tests. A qualitative representation provides adiagnostic tool that may suffice in all but the most complicated ofdiagnostic situations, such as situations in which a user is attemptingto characterize and understand a major fault in the system. However, asreliability in electrodes 38 and leads 24 tends to be very high, asimple qualitative representation may, in the overwhelming majority ofsituations in which there is no issue with electrodes 38 or leads 24,provide the best and most useful data to a user, indicating either thateverything is OK, or that there may be issues that need to be followedup on with a quantitative diagnostic with quantitative representations.

In the case of the embodiment depicted in FIG. 3D, the qualitativerepresentation is a binary representation, as it simply shows the numberof electrodes 38 that are “OK”, with the remainder of electrodes 38 notindicated as being “OK” being bad. Various contemplated embodiments flipthe binary representations, with “bad” being displayed on display 52along with the number of “bad” electrodes. Additionally, alternative,largely-synonymous terminology is also contemplated, for instancesubstituting “good” or “functional” for “OK”. Further embodimentsutilizing trinary qualitative representations are likewise contemplated,which may, for instance, include

FIG. 4 depicts a block diagram of controller 32. Primary coil 70 enablescontroller 32 to establish an inductive communication link withimplantable neurological stimulator 22 via secondary coil 23 whenprimary coil 70 is placed in proximity of secondary coil 23 (in anembodiment, within 6.0 centimeters). Battery 74 provides direct currentpower to electronics 72. In various embodiments, battery 74 may berechargeable or disposable, as batteries may improve patient safety byforeclosing the possibility of electrical failure creating an opencircuit between patient 30 and a wall outlet. Alternatively, battery 74may be substituted with power supplied by an outside source, eitherincluding a power converter as a component of controller 32, allowingcontroller 32 to run off of AC power directly from a standard outlet, oran embodiment may require input power be converted to suitableproperties prior to arriving at controller 32.

Controller 32 additionally includes various electronics 72. Electronics72 include various modules, including control module 76 which, in anembodiment, comprises, at least in part, off-the-shelf hardwarecomponents such as a processor and a memory module, as well ascustom-designed componentry used in controlling the various componentsof controller 32, as well as conducting electrode impedance tests.Interface module 78 may be operatively coupled to coil 70 and controlmodule 76 and include componentry for sending and receiving informationvia coil 70, including transmit and receive circuits known in the art.Electronics 72 are likewise operatively coupled to battery 74, display52 and input buttons 54.

FIG. 5 shows a flowchart depicting the function of controller 32. When amedical professional commences (100) a lead impedance test via inputbuttons 54, control module 76 determines if an inductive link has beenestablished (102) between coil 70 and implantable neurologicalstimulator 24. If an inductive link has not been established, controlmodule 76 may wait (104) and periodically check if an inductive link hasbeen established (102), repeating as necessary until a timeout conditionoccurs.

If an inductive link has been established, control module establishes(106) pairs of electrodes 38 that will be tested for impedance.Electrode 38 pairs may be created utilizing a variety of differentmethods, depending on the particular circumstances of the test. In anembodiment, each subject electrode 38 is included in a total of twopairs, with the other electrode in each pair being selected from any ofthe other electrodes 38 assigned to the same group of four as subjectelectrode 38 (see FIG. 2). In this embodiment, electrodes 38 are pairedwith electrodes 38 with adjacent identifier numbers, or, if electrode 38is either the first or the last electrode 38 in a group, with theelectrode 38 in the group that is adjacent as well as the other endelectrode 38 in the group. In this embodiment, electrodes 38 are pairedwith only two other electrodes 38. In an alternative embodiment, eachelectrode 38 is paired with each other electrode 38 in its group.

The above described embodiment avoids potential issues commonlyencountered in electrode impedance testing. In addition to simplifyingthe selection of electrode pairs, the grouping of electrodesautomatically avoids certain potential hazards, such as testing forimpedance between electrodes that are on opposite sides of a patient's30 brain, in an embodiment where implantable neurological stimulator issubstituted for a deep brain stimulator. The above embodiment likewisehelps with patient safety and comfort by ensuring that electrodes 38that are tested as pairs are in close proximity of each other, therebypreventing long current paths over potentially sensitive area's ofpatient's 30 body.

Further, by only testing each electrode 38 twice, the above-describedembodiments tend to reduce test time compared with impedance tests thattest each electrode 38 with every other electrode 38. These embodimentsalso tend to save on battery 74 power by reducing the amount of energyused to conduct the impedance testing. However, in spite of the savingsof time and energy, these embodiments do not lead to any reducedaccuracy in determining basic qualitative function of electrodes 38.Because each electrode 38 is tested against two other electrodes 38

Further embodiments are envisioned where each electrode is tested onlyonce, thereby further reducing the amount of time to conduct testing dueto approximately halving the number of impedance tests conducted, aswell as reducing and the amount of energy consumed. The informationderived from such testing, however, may only be precise to indicate afailure in at least one of the two electrodes 38 tested, rather than afailure in a particular electrode 38. However, in situations where auser is only concerned with whether the system as a whole may beexperiencing any failures, rather than which, if any, individualelectrodes 38 are experiencing failures, the decrease in precisequalitative information may be irrelevant, while still yielding thebenefit of reduced test time and reduced energy consumption.

After the electrode pairs have been selected, the first such pair istested (108). Using Ohm's Law, control module 76 determines if theimpedance between the electrode 38 pair is within (110) thepredetermined allowable range by placing a voltage, or sending a currentdown, one of the electrodes 38 of the pair, measuring the voltage orcurrent on the other electrode of the pair, and then utilizing Ohm's Lawto determine the impedance. If the measured impedance is within (110) apredetermined range then controller 32 records (112) a note indicatingthat the electrode pair passed. If the measured impedance is outside ofthe predetermined range then controller 32 records (114) a note that theelectrode pair failed. In an embodiment, controller 32 records resultsfrom steps (112) and (114) in a memory module in electronics 72. If allelectrode pairs have not yet been tested (116) the next electrode pairis then tested (118).

If all electrode pairs have been tested then controller 32 determinesand displays (118) the results. Results are determined by checking theresults for each electrode 38. In an embodiment, for each electrode thatwas part of one or no electrode pairs 38 that failed (114), a counter isincremented by one. For each electrode 38 that has two failures, thecounter is not incremented. After all electrodes 38 have been accountedfor, the value of the counter, which indicates the number of electrodesthat have passed, may be displayed on display 52, along with anindication that the number represents the number of electrodes 38 thathave passed the impedance test.

Alternate embodiments could display the actual impedance value with theuser scrolling the list of measurements, and use a variety of upper andlower limits for advanced troubleshooting, e g., greater than 3,600ohms, greater than 5,000 ohms or greater than 10,000 ohms. However, ascontroller 32 may primarily be designed to be used in preliminarytesting to either verify that all electrodes 38 are operable andadequately positioned, or to detect the existence of a fault condition,such an alternate embodiment may not commonly be available to a user.

Thus, embodiments of the controller for obtaining prescriptive analysisof functionality of implantable medical device leads, system and methodtherefore are disclosed. One skilled in the art will appreciate that thepresent invention can be practiced with embodiments other than thosedisclosed. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present invention is limitedonly by the claims that follow.

What is claimed is:
 1. A controller for an implantable medical devicehaving a plurality of electrodes, said implantable device being capableof delivering a therapeutic stimulation to a patient, comprising: acontrol module; a user interface providing control of said controlmodule by a medical professional; an electrode interface operativelycoupled between said plurality of electrodes and said control module;wherein said control module uses said electrode interface to obtain aplurality of measurements of impedance values for a plurality ofselected pairs of individual ones of said plurality of electrodes;wherein said user interface displays an indicia, indicative ofoperability of a group of at least one of said plurality of electrodes,based on a comparison of said plurality of measurements to apredetermined range, said indicia being a qualitative representation ofoperability of said group of at least one of said plurality ofelectrodes; wherein said implantable medical device further comprises aplurality of leads, each of said plurality of electrodes beingassociated with one of said plurality of leads, wherein each of saidplurality of electrodes of each individual one of said plurality ofselected pairs of electrodes are associated with the same lead, andwherein said control module uses said electrode interface to obtain aplurality of measurements of impedance values for said plurality ofselected pairs.
 2. A controller as in claim 1 wherein said indicia is afirst indicia, and wherein said user interface displays a second indiciaupon a different result of said comparison.
 3. A controller as in claim2 wherein said user interface displays said first indicia if saidcomparison determines that all of said plurality of measurements ofimpedance values are within said predetermined range.
 4. A controller asin claim 3 wherein said user interface displays a second indicia if saidcomparison determines that any of plurality of measurements of impedancevalues are outside of said predetermined range.
 5. A controller as inclaim 1 wherein said controller includes one of said plurality ofelectrodes not more than twice in said plurality of measurements ofimpedance values of selected ones of said plurality of electrodes.
 6. Acontroller as in claim 1 wherein said controller conducts said pluralityof measurements of impedance values for fewer than all of said pluralityof electrodes.
 7. A controller as in claim 6 wherein said controllerconducts said plurality of measurements of impedance values only forthose of said plurality of electrodes that are in use for saidtherapeutic stimulation.
 8. A controller as in claim 1 wherein saidpatient has a brain having two hemispheres, each of said plurality ofelectrodes being associated with one of said hemispheres, wherein eachof said plurality of electrodes of each of said plurality of selectedpairs of electrodes are associated with a same one of said hemispheresof said brain.
 9. A controller as in claim 2 wherein said controllerassociates each individual one of said plurality of electrodes with twoof said plurality of selected pairs, and wherein said second indicia isdisplayed for an individual one of said plurality of electrodes only ifeach of said measurements of impedance of said plurality of selectedpairs with which said individual one of said plurality of electrodes isassociated are outside of said predetermined range.
 10. A controller asin claim 1 wherein said qualitative representation is a binaryqualitative representation.
 11. A system capable of delivering atherapeutic stimulation to a patient, comprising: an implantable medicaldevice having a plurality of electrodes capable of delivering saidtherapeutic stimulation to said patient; and a controller, operativelycoupled to said implantable medical device, comprising: a controlmodule; a user interface providing control of said control module by amedical professional; an electrode interface operatively coupled betweensaid plurality of electrodes and said control module; wherein saidcontrol module uses said electrode interface to obtain a plurality ofmeasurements of impedance values for a plurality of selected pairs ofindividual ones of said plurality of electrodes; wherein said userinterface displays an indicia, indicative of operability of a group ofat least one of said plurality of electrodes, based on a comparison ofsaid plurality of measurements to a predetermined range, said indiciabeing a qualitative representation of operability of said group of atleast one of said plurality of electrodes; and wherein said implantablemedical device further comprises a plurality of leads, each of saidplurality of electrodes being associated with one of said plurality ofleads, wherein each of said plurality of electrodes of each individualone of said plurality of selected pairs of electrodes are associatedwith the same lead, and wherein said control module uses said electrodeinterface to obtain a plurality of measurements of impedance values forsaid plurality of selected pairs.
 12. A system as in claim 11 furthercomprising a remote station, said remote station being operativelycoupled to said controller, said implantable medical device beingoperatively coupled to said remote station via far-field radio frequencycommunication.
 13. A method for delivering therapeutic stimulation to apatient using an implantable medical device having a plurality ofelectrodes, comprising the steps of: obtaining a plurality ofmeasurements of impedance values for a plurality of selected pairs ofindividual ones of said plurality of electrodes; and displaying anindicia based upon a result of a comparison of said plurality ofmeasurements of impedance values with a predetermined range, saidindicia being indicative of operability of a group of at least one ofsaid plurality of electrodes, said indicia being a qualitativerepresentation of operability of said group of at least one of saidplurality of electrodes; wherein said implantable medical device furthercomprises a plurality of leads, each of said plurality of electrodesbeing associated with one of said plurality of leads, wherein each ofsaid plurality of electrodes of each individual one of said plurality ofselected pairs of electrodes are associated with a same lead, andwherein said obtaining step obtains a plurality of measurements ofimpedance values for said plurality of selected pairs.
 14. A method asin claim 13 wherein said indicia is a first indicia, further comprisingthe step of displaying a second indicia upon a different result of saidcomparison.
 15. A method as in claim 13 wherein said displaying stepdisplays said first indicia if said comparison determines that all ofsaid plurality of measurements of impedance values are within saidpredetermined range.
 16. A method as in claim 13 wherein said displayingstep displays a second indicia if said comparison determines that any ofplurality of measurements of impedance values are outside of saidpredetermined range.
 17. A method as in claim 16 wherein said firstindicia represents an operable state and wherein said second indiciarepresents a non-operable state.
 18. A method as in claim 14 whereinsaid obtaining step obtains one of said plurality of measurements ofimpedance values for one of said plurality of electrodes only once. 19.A method as in claim 14 wherein said obtaining step obtains saidplurality of measurements of impedance values for fewer than all of saidplurality of electrodes.
 20. A method as in claim 19 wherein saidobtaining step obtains said plurality of measurements of impedancevalues only for those of said plurality of electrodes that are in usefor said therapeutic stimulation.
 21. A method as in claim 14 whereinsaid patient has a brain having two hemispheres, each of said pluralityof electrodes being associated with one of said hemispheres, whereineach of said plurality of electrodes of each of said plurality ofselected pairs of electrodes are associated with a same one of saidhemispheres of said brain.
 22. A method as in claim 13, wherein eachindividual one of said plurality of electrodes is associated with two ofsaid plurality of selected pairs, and wherein said displaying stepdisplays said second indicia for an individual one of said plurality ofelectrodes only if each of said measurements of impedance of saidplurality of selected pairs with which said individual one of saidplurality of electrodes is associated are outside of said predeterminedrange.
 23. A method as in claim 14 wherein said first indicia is basedon a number of measured impedance values measured either within oroutside of said predetermined range.